It is known from the state of the art to use skimming devices, also called skimmers, to remove a fluid with a low density spread over the surface of another fluid with a higher density, or primary fluid. The primary fluid is for example a petrochemical or chemical fluid contained in a tank or by digression, a large expanse of liquid such as an ocean.
The low-density fluid is generally a fluid that one wishes to separate from the primary fluid to next discharge it, then store it in an auxiliary tank for later use or for later depollution treatment to make it less harmful for humans and/or to recycle it. The low-density fluid can also be a foam or a pollutant that one wishes to separate from the primary fluid, then discharge to a specific sewer.
Among the existing skimming devices, the device described in French application FR 2,452,549 includes a spillway intended to collect the surface fluid and a vat intended to discharge said fluid toward the storage tank. The surface fluid is sent toward the vat when a nappe occurs at the threshold of the spillway. One drawback of this device is that it does not allow precise collection of only the surface fluid. Indeed, as long as the thickness of the fluid situated on the surface is relatively large, the device can skim it without difficulty. Conversely, once the interface between the surface fluid and the primary fluid becomes too small, the device will skim both the surface fluid and the primary fluid.
Likewise, but in the case of use in an offshore marine environment, the device for recovering a petrochemical surface layer described by American U.S. Pat. No. 3,745,115 makes it possible, through the presence of holes arranged in the outer framework of its structure, to collect, then discharge a seawater-oil mixture. In the case at hand, this device does not make it possible to collect and discharge only the petrochemical layer present on the surface of the seawater.
Consequently, once the skimming operation is complete, these devices cannot prevent and/or prohibit accidental or untimely skimming of a certain volume of primary fluid.
In Dutch patent application NL 7,713,456, the disclosed skimming device comprises a valve able to be actuated based on the height of the surface fluid present in the fluid storage vat.
Furthermore, the large majority of skimmers used to treat storage vats are kept in position using one or several guiding posts installed permanently in the vat.
These guiding posts have the drawbacks of being cumbersome and not removable. They therefore cannot be used for floating roof vats, vats whose height is intended to vary based on the volumes of fluids present inside.
Consequently, these guiding posts are intended to stabilize the skimmer horizontally and vertically when it rests on a layer of surface fluid.
However, when the skimmer is for example stabilized using a mechanical connection of the ball and socket joint type or the linear rectilinear type, or using a flexible coupler, destabilization may occur, and from there, blocking of the device during the skimming operation.